It is well known that excessive moisture in buildings causes considerable problems. Drywall and flooring absorb moisture and are readily damaged if the excessive moisture condition persists for any length of time. Interior elements such as insulation, studs, and joists can eventually be affected as well. Furthermore, mold begins to form on the damp building materials, and can remain in the structure even after it has dried, causing breathing problems for persons occupying the building.
At the extreme, such excessive moisture conditions are exemplified by a flooded building. U.S. Pat. No. 6,457,258 to Cressy et al., “Drying Assembly and Method of Drying for a Flooded Enclosed Space”, discloses an apparatus for drying flooded buildings that overcomes problems in the prior art. Such prior art is said to require stripping wall and floor coverings and using portable dryers to circulate air to dry out the exposed floor boards, joists and studs. The methods were slow and allowed mold to form on the interior framing, which could then go unnoticed and be covered up and then later present a health hazard to occupants.
The solution proposed by Cressy is to introduce very hot and dry air into the building, indicated as being at 125° F. and 5% relative humidity, in order to dry the building very quickly to prevent mold growth and allow an early return to occupants. In the apparatus of Cressy et al., outside air is heated by a furnace and the heated air is blown into the building where it picks up moisture and then is exhausted back outside. In Cressy heat from the warmer exhaust air is transferred to the cooler outside air prior to heating by the furnace, thereby increasing the efficiency of the system.
U.S. Pat. No. 6,647,639 to Storrer, “Moisture Removal System”, addresses the problem of extracting water promptly to prevent the formation of rot, mold, rust and the like in flooded buildings. Storrer reveals the prior art as including passive drying through opening windows, etc. and active drying using forced air (heated or not) to expedite evaporation. Storrer discloses using a blower to blow (or draw) dry air through a hose and manifolds that can be directed at a particular area that it is desired to dry.
In a similar vein, U.S. Pat. No. 5,960,556 to Jansen, “Method for Drying Sheathing in Structures”, is directed to drying walls with warm, low humidity air.
Prior art systems for drying flooded buildings also include dessicant dehumidifiers that use a desiccant material with a high affinity to water to absorb water from the air, and refrigerant dehumidifiers that condense water out of the air by cooling it. In both of these systems, the water must be disposed of in some manner. The water absorbed by the dessicant material is removed by subsequently drying the material. The water condensed by the refrigerant system is collected in a reservoir that must be emptied from time to time or piped to a disposal area. Care must be taken that the collected water be removed so that mold does not form therein and disperse within the building.
While flooded buildings demonstrate an extreme situation, excessive moisture also causes problems in other situations as well. During construction wet conditions are often present in buildings. Long periods of rain during construction, burst pipes, wet building materials (such as concrete), and like conditions can contribute to humid conditions where excessive moisture can be absorbed by joists and studs. These moist members are often covered up by flooring and drywall such that drying is prevented, and rot, mold, and the like can form.
In cold climates it is also common to use construction heaters to warm buildings during construction. Such heaters that use combustion inside the building also cause a significant increase in the humidity of the air inside the building, contributing to excessive moisture inside walls and floors and the problems associated therewith.
Once the building is completed the problems remain. Mold formed inside the walls and floors can grow and cause health problems for occupants. Rot can continue once started and cause premature structural failure.
The opposite condition of excessively dry air in a building can cause problems as well. Excessively dry air can draw moisture out of wood causing warping and splitting of floors and millwork.